Question: 6 binders cost $11.70. Which equation would help determine the cost of 2 binders?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 6 binders. We want to know the cost of 2 binders. We can write the numbers of binders as a proportion: $\dfrac{6}{2}$ We know 6 binders costs $11.70. We can let $x$ represent the unknown cost of 2 binders. The proportion of these costs can be expressed as: $\dfrac{\$11.70}{x}$ The cost changes along with the number of binders purchased, and so the two proportions are equivalent. $\dfrac{6}{2} = \dfrac{\$11.70}{x}$